Anti-vibration rubbers are conventionally used in the field of vehicles, general industrial machinery and the like for preventing vibration, noise and the like occurring in an engine, a vehicle body and the like. Performances required of the anti-vibration rubbers include a low dynamic magnification.
In order to improve the anti-vibration performance of an anti-vibration rubber, it is effective that the dynamic magnification (dynamic spring constant (Kd)/static spring constant (Ks)) of an anti-vibration rubber composition corresponding to an anti-vibration member has a sufficiently small value. Accordingly, as the dynamic spring constant obtained in a vibration state where the vibration of a vehicle engine or the like is transmitted is smaller and as the static stiffness corresponding to the support performance of the engine, the vehicle body and the like, namely, the static spring constant, is larger, higher anti-vibration performances can be attained. Therefore, conventionally, a composition comprising a single natural rubber having a low dynamic magnification and high strength or a blended rubber containing a natural rubber as a main component together with a diene synthetic rubber such as a butadiene rubber or a styrene butadiene rubber as a rubber component and a carbon black.
For example, JP 8-269239 A has proposed, for reducing the dynamic magnification of an anti-vibration rubber, a method in which a carbon black having a specific nitrogen absorption specific surface area and dibutyl phthalate oil absorption number is added to a natural rubber used as a rubber component.
For example, JP 8-73658 A has proposed, for reducing the dynamic magnification, a method in which carbon black is added to a rubber component of an isoprene-based rubber and a butadiene rubber as a rubber composition of an anti-vibration rubber.
For example, JP 2006-143859 A has proposed, for attaining both durability and a low dynamic magnification, a method in which a diene rubber, a hydrazine derivative and a carbon black are contained in an anti-vibration rubber composition.
For example, JP 2011-105870 A has proposed, for attaining both high durability and a low dynamic magnification, also a method in which a carbon black and a silica are contained in a specific amount ratio in a diene rubber as an anti-vibration rubber composition.